Apparatus and method for controlling recording and reproduction in digital video cassette tape recorder

ABSTRACT

An apparatus and method for controlling recording and reproduction in a video cassette tape recorder are disclosed apparatus is capable of, in a recording mode, separating specific data for speed-varied reproduction from compressed digital video signals, recording them on designated tracks, recording position information of the designated tracks on a control track by an index head or recording position information of recording position-synchronized blocks at the starting portions of the designated tracks recorded with the specific data, and in a speed-varied reproduction mode, controlling a capstan servo speed so as to maintain the travel of a magnetic tape at a normal speed and periodically or non-periodically accelerate or decelerate it where specific data for varied-speed have been recorded periodically or non-periodically on predetermined portions of tracks, thereby making heads travel repeatedly at the normal speed and the high speed and thereby detect continuously the specific tracks for varied-speed. A repeatability of reproduced video at a varied speed is obtained without any deterioration in picture quality, because of recording of the specific data for speed-varied reproduction and the continuous detection of the specific data in the speed-varied reproduction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a circuit device and method forcontrolling recording and reproduction in a digital cassette taperecorder.

2. Description of the Background Art

For analog/digital conversion for converting an analog video signal intoa digital video signal and linear quantization, a signal transmissionrate of about 100 Mega bits per second is typically required in the caseof a normal TV broadcast signal such as NTSC, SECAM and PAL signals. Onthe other hand, a high definition TV (HDTV) signal with higherresolution than that of the normal TV broadcast signal requires a signaltransmission rate higher than 100 Mega bits.

For achieving data transmission in a limited transmission band,digitalized video signals should be transmitted in the form compressedin accordance with the video data compression-technique. In the case ofdigital cassette tape recorders (digital VCRs) having a limitation onrecord bandwidth, signals recorded on a magnetic tape may be digitalnormal TV signals having the form of compressed signals or digital HDTVsignals having the form of compressed signals.

Referring to FIG. 1, there is illustrated a conventional recordingcircuit for such a digital VCR. As shown in FIG. 1, the recordingcircuit includes an interface 1 for converting a compressed digitalvideo signal into a signal having the recordable form, an interleavingand channel-dividing circuit 2 for interleaving an output V1 from theinterface 1 in a predetermined form to reduce burst error andchannel-dividing it to be matched with the zero bandwidth of a recordingchannel, recording formatters 3A and 3B for respectively convertingoutputs V2 and V3 of the interleaving and channel-dividing circuit 2 torecord formats each including a synchronous signal, an identificationsignal and redundancy bits for error correction codes, channelmodulators 4A and 4B for modulating outputs V4 and V5 of the recordingformatters 3A and 3B, respectively, recording amplifiers 5A and 5B foramplifying outputs V6 and V7 of the channel modulators 4A and 4B,respectively, a drum pulse generator 7 for outputting two pulses atevery rotation of a head drum 6 caused by driving a drum motor M1, andswitches SW1 and SW2 for performing their switching operations based onan output SWP from the drum pulse generator 7 to selectively transmitoutputs V8 and V9 of the recording amplifiers 5A and 5B to heads HD1 (orHD3) and HD2 (or HD4), respectively. In FIG. 1, the reference numeral 8denotes a guide pin, 10 a pinch roller, and 9 a capstan adapted to berotated by a capstan motor M2.

FIG. 2 is a block diagram illustrating a conventional reproductioncircuit for the digital VCR. As shown in FIG. 2, the reproductioncircuit includes reproduction amplifiers 11A and 11B for receivingoutputs from selected heads HD1 (or HD3) and HD2 (or HD4) mounted on thehead drum 6 via the switches SW1 and SW2 switched in accordance with theoutput SWP from the drum pulse generator 7 and amplifying them,respectively, equalizers 12A and 12B for compensating distortions offrequency characteristics of outputs V10 and V11 of the reproductionamplifiers 11A and 11B, respectively, channel demodulators 13A and 13Bfor demodulating outputs V12 and V13 of the equalizers 12A and 12B,respectively, sync-detecting and error-correcting circuits 14A and 14Bfor detecting synchronous signals SYNC added in a recorded signal fromthe outputs V14 and V15 of the channel demodulators 13A and 13B andcorrecting errors of the outputs V14 and V15, respectively,deinterleaving circuits 15A and 15B for deinterleaving outputs V16 andV17 of the sync-detecting and error-correcting circuits 14A and 14B intothe original signal form, respectively, a deformatter 16 for recoveringoutputs V18 and V19 of the deinterleaving circuits 15A and 15B to theoriginal signal format, and an interface 17 for converting an output V20of the deformatter 16 into a reproduced digital signal Vo and outputtingit.

Now, operations of the conventional circuits will be described inconjunction with FIGS. 1 to 6.

First, in a recording mode, a compressed HDTV signal or compressednormal TV signal is applied to the interface 1 which, in turn, convertsthe received signal into a signal V1 capable of being recorded andreproduced. The signal V1 is then interleaved into a predetermined formto reduce burst errors in the interleaving and channel-dividing circuit2 which, in turn, outputs signals V2 and V3 channel-divided so as to bematched with the bandwidth of the recording channel.

The outputs V2 and V3 from the interleaving and channel-dividing circuit2 are applied to the recording formatters 3A and 3B and then added withsynchronous signals SYNC, identification signals ID and redundancy bitsfor error correction codes ECC in the recording formatters 3A and 3B.Resultant signals from the recording formatters 3A and 3B are thenreceived in the channel modulators 4A and 4B which, in turn, outputsignals V6 and V7 matched with a predetermined recording format,respectively. The outputs V6 and V7 from the channel modulators 4A and4B are applied to the recording amplifiers 5A and 5B which, in turn,amplify them, respectively.

Outputs V8 and V9 from the recording amplifiers 5A and 5B are applied toselected heads HD1 (or HD3) and HD2 (or HD4) via the switches SW1 andSW2 switched by the output SWP from the drum pulse generator 7, so thatthey are recorded on a magnetic tape in a recording format shown in FIG.3.

In this case, the drum pulse generator 7 generates two pulses at everyrotation of the head drum 6 driven by the drum motor M1.

Meanwhile, frames have a mixed form of intra-frames (I-frames) able tobe independently decoded and predictive frames (P-frames) compressed bymoving information of previous screen and unable to be independentlydecoded, in accordance with a video compression system for HDTV signalsor an MPEG (Moving Picture Experts Group) system. Bit rate generated ineach frame is non-uniform, as shown in FIG. 5.

In a reproduction mode, the magnetic tape travels by the rotation of thecapstan 9 caused by the capstan motor M2 while being in contact with thehead drum 6 rotating by the driving force of the drum motor M1. At thistime, the heads HD1 (or HD3) and HD2 (or HD4) detect signals on themagnetic tape and send them to the reproduction amplifiers 11A and 11Bvia the switches SW3 and SW4 switched by the output SWP of the drumpulse generator 7, respectively.

The signals received in the reproduction amplifiers 11A and 11B areamplified to a predetermined level and then sent to the equalizers 12Aand 12B which, in turn, output signals V12 and V13 having compensatedfrequency characteristics, respectively. The signals V12 and V13 fromthe equalizers 12A and 12B are then applied to the channel demodulators13A and 13B, respectively, so as to be demodulated. Outputs V14 and V15from the channel demodulators 13A and 13B are received in thesync-detecting and error-correcting circuits 14A and 14B which, in turn,detect respectively synchronous signals SYNC and identification signalsID from synchronous block of the received signals and remove errorcomponents included in the data.

Outputs V16 and V17 from the sync-detecting and error-correctingcircuits 14A and 14B are applied to the deinterleaving circuit 15A and15B which, in turn, deinterleave the signals V16 and V17 and therebygenerate signals V18 and V19 having the original signal forms,respectively. The signals V18 and V19 are received in the deformatter 16and thereby converted to the format having the signal form prior torecording. Signal V20 from the deformatter 16 is applied to theinterface 17 which, in turn, generates a reproduced digital signal Vo.

In a speed-varied reproduction, the rotation speed of the head drum 6 iskept constant while the travel of the magnetic tape is accelerated. As aresult, the heads HD1 to HD4 travel across tracks on the magnetic tape.The trace of the heads is shown in FIG. 3. Consequently, the detectedsignals have a discontinuous data form, namely, data burst with amagnitude inversely proportional to the travel speed of the magnetictape.

In the case of existing analog VCRs, data of one field are recorded inone track in the reproduction order. Accordingly, regions on tracks fromwhich data are detected in the speed-varied reproduction mode aredirectly associated with reproduction regions of a corresponding screen.Therefore, video reproduction in the speed-varied mode is possible evenwhen a noise bar is generated due to data detected on an adjacent track.

In the case of existing digital VCRs, however, data of one field arerecorded in a plurality of tracks, as shown in FIG. 3. As a result,reproduction bursts on adjacent tracks have no relation with thereproduction order. In this case, therefore, a frame memory and anaddressing process for rearranging data detected are needed.Furthermore, there is a problem of an inevitable mosaic-shapeddistortion of small segments due to discontinuous detection of databursts.

For a video reproduction in the existing digital VCRs, data burstsdetected should be independently decoded. However, these data burstsinclude unrecoverable other data on the screen or unrecoverable previousscreen data, because the data bursts have the digital form compressedusing the correlation between signals that may be the important factorof adversely affecting the picture quality in reproduction. Theunrecoverable data can not be decoded and thereby reproduced in the formof videos. In particular, such a problem becomes more frequent in thecase of data obtained from the video compression system such as thevariable length coding involving non-uniform data lengths.

In other words, although data bursts detected from tracks on which dataof the 0-th I-frame, the n-th I-frame, the 2n-th I-frame . . . arerecorded can be constructed to a video, data bursts detected from trackson which data of P-frames are recorded can not be constructed to avideo.

SUMMARY OF THE INVENTION

Therefore, an object of the invention is to provide an apparatus andmethod for controlling recording and reproduction in a digital VCRcapable of, in a recording mode, extracting independently-decodabledata, namely, intra-frames from digital signals having a compressed formso as to record them on tracks designated with respect to a number ofdifferent tape speeds and, in a speed-varied reproduction mode,repeatedly performing a normal-speed travel and a high-speed travel of amagnetic tape so as to detect specific data for speed-variedreproduction periodically or non-periodically recorded on tracks of themagnetic tape, thereby reproducing videos with improved picture quality.

In accordance with the present invention, this object can beaccomplished by providing an apparatus for controlling recording andreproduction in a video cassette tape recorder comprising: frameextracting means for buffering and amplifying compressed digital datainput, and extracting specific data for a speed-varied reproduction fromthe compressed digital data; frame recording position controlling meansfor calculating the number of tracks for the compressed digital data,selectively outputting a buffered and amplified output and the extractedspecific data from said frame extracting means, and outputting amultiplexing timing signal; frame position information recording meansfor recording position information of tracks for a speed-variedreproduction and index information on a magnetic tape, based on themultiplexing timing signal; digital recording means for recording thedigital signals including the index information on the magnetic tape;digital reproduction means for reproducing the digital signals recordedon the magnetic tape; frame position information detecting means fordetecting position information of specific tracks for the speed-variedreproduction and index information tape speed controlling means forcontrolling the speed of a capstan motor, based on the detected indexinformation and position information of the specific tracks; and frameremoving means for receiving therein the output from the digitalreproduction means and removing unnecessary bit streams from thespecific data. Further scope of applicability of the present inventionwill become apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the invention willbecome more apparent upon a reading of the following detailedspecification and drawings which are given by way of illustration only,and thus are not limitative of the present invention, in which:

FIG. 1 is a block diagram of a conventional recording circuit for adigital VCR;

FIG. 2 is a block diagram of a conventional reproduction circuit for adigital VCR;

FIG. 3 is a schematic view illustrating recording tracks of a magnetictape and a trace of heads travelling in a speed-varied reproduction modein accordance with the conventional art;

FIG. 4 is a schematic view illustrating a correlation among frames inaccordance with a video compression system;

FIG. 5 is a schematic view illustrating an encoded bit stream;

FIG. 6 is a schematic view illustrating synchronous blocks of a videosignal for recording and reproduction;

FIG. 7 is a block diagram of a recording control circuit for a digitalVCR in accordance with an embodiment of the present invention;

FIG. 8 is a block diagram of a reproduction control circuit for adigital VCR in accordance with an embodiment of the present invention;

FIG. 9 is a schematic view illustrating recording tracks in accordancewith the present invention;

FIGS. 10A to 10D are waveform diagrams of signals generated in recordingposition control;

FIG. 11 is a schematic view illustrating recording position-synchronizedblocks in accordance with the present invention;

FIG. 12 is a flow chart illustrating a frame detection procedure inaccordance with the present invention;

FIGS. 13A to 13C illustrate a capstan servo speed control in accordancewith the present invention; and

FIGS. 14A to 14D are waveform diagrams of signals generated in frameremoval.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 7 and 8, there is illustrated an apparatus forcontrolling recording and reproduction in a digital VCR in accordancewith an embodiment of the present invention.

FIG. 7 is a block diagram illustrating a recording control circuitdevice for a digital VCR in accordance with the present invention. Asshown in FIG. 7, the recording control circuit device includes a frameextracting unit 20 for buffering and amplifying an output signal V1,namely, compressed digital data, of an interface 1, and extractingspecific data for speed-varied reproduction from the received signal V1,a frame recording position controlling unit 21 for selectivelyoutputting an output V22 of the frame extracting unit 20 obtained afterthe buffering and amplifying operations and the extracted specific dataV23, and outputting a multiplexing timing signal V27', a frame positioninformation recording unit 19 for recording track position informationand index information for speed-varied reproduction on a magnetic tape,based on the multiplexing timing signal V27', and a digital recordingunit for recording the digital data including the index information onthe magnetic tape.

In similar to the conventional case, the digital recording unit 18includes an interleaving and channel-dividing circuit 2, recordingformatters 3A and 3B, channel modulators 4A and 4B, recording amplifiers5A and 5B, a head drum 6 equipped with heads HD1 to HD4, a drum pulsegenerator 7 and switches SW1 and SW2. With this construction, thedigital recording unit 18 records digital signals including indexsignals on the magnetic tape. For simplicity of the description, thedescription concerning the digital recording unit 18 will be omitted.

The frame extracting unit 20 includes a buffer 22 adapted to buffer theoutput signal V1 of the interface 1 and thereby amplify it to apredetermined level, a frame detector 24 adapted to detect specific datacorresponding to an intraframe, and a frame memory 23 adapted to storethe detected specific data.

The frame recording position controlling unit 21 includes a track numbercalculator 28 adapted to calculate the number of tracks, a multiplexingtiming generator 27 adapted to operate an output SWP of the drum pulsegenerator 7 and thereby generate a multiplexing timing signal V27, a bitstuffing circuit adapted to make the output signal V23 of the framememory 23 have a constant data length when the output signal V23 is atan underflow state, and a multiplexer 25 adapted to multiplex the outputsignals V22 and V23 of the frame extracting unit 20 and thereby output asignal V25.

On the other hand, the frame position information recording unit 19includes a frame position recorder 29 adapted to receive themultiplexing timing signal V27' from the frame recording positioncontrolling unit 21 and record, on the leading portion of a track forvaried speed, position information of a next track for speed change, andan index signal recorder 30 adapted to record index information of atrack to be scanned by an index head 31.

In FIG. 7, the reference numeral 8 denotes a guide pin, 9 a capstanengaged with a pinch roller 10, M1 a drum motor, and M2 a capstan motor.

FIG. 8 is a block diagram illustrating a reproduction circuit device inaccordance with the present invention. As shown in FIG. 8, thereproduction circuit includes a digital reproduction unit 32 forreproducing compressed digital data recorded on the magnetic tape, aframe position information detecting unit 33 for detecting indexinformation from the magnetic tape and detecting information indicativeof the position of a specific track, a tape speed controlling unit 34for controlling the speed of the capstan motor M2, and a frame removingunit 35 for a removing specific data for speed-varied reproductionduring a reproduction at a constant speed.

The digital reproduction unit 32 includes the head drum 6 equipped withthe heads HD1 to HD4, the drum pulse generator 7, switches SW3 and SW4,reproduction amplifiers 11A and 11B, equalizers 12A and 12B, channeldemodulators 13A and 13B, and sync-detecting and error-correctingcircuit 14A and 14B. This construction of the digital reproduction unit32 is similar to that of the conventional digital reproduction unitshown in FIG. 2. Therefore, the detailed description concerning thedigital reproduction unit 32 will be omitted for simplicity of thedescription.

The frame position information detecting unit 33 includes an indexsignal detector 36 adapted to detect index information, a recordingposition-synchronized block detector 40 adapted to detect, from theoutputs V16 and V17 of the sync-detecting and error-correcting units 14Aand 14B, position information of a specific track including specificdata recorded, and a recording position decoder 39 adapted to decode thedetected position information.

The tape speed controlling unit 34 includes a capstan servo-speedcalculating circuit 38 adapted to operate outputs V36 and V39 of theframe position frame detecting unit 33, and a drive signal generator 37adapted to generate a drive signal V37 for controlling the speed of thecapstan motor M2.

Finally, the frame removing unit 35 includes a frame removal timinggenerator 41 adapted to operate an output of the drum pulse generator 7and outputs V36 and V39' of the frame position information detectingunit 33 and thereby generate a timing signal for removing specific datafor speed-varied reproduction, a stuffing bit-detecting and removingcircuit 42 adapted to detect and remove a stuffing bit added forpreventing generation of the underflow of the frame memory 23, and adeformatter 16 adapted to convert an output of the digital reproductionunit 32 to the format having the signal form prior to recording.

Operations of the apparatus for controlling recording and reproductionin the digital VCR in accordance with the present invention will bedescribed, in conjunction with FIGS. 4 to 14.

First, in a recording mode, an input signal Vi such as a compressed HDTVsignal or compressed normal TV signal is applied to the interface 1which, in turn, converts the received signal into a signal Vl having theform capable of being recorded and reproduced.

The signal V1 from the interface 1 is then applied to the frameextracting unit 20. In the frame extracting unit 20, the received signalV1 is buffered and amplified by the buffer 22. By the buffering andamplifying operations, the signal V1 is delayed for a predeterminedtime. The frame detector 24 detects compressed I-frames repeated atintervals of n frames, from a bit stream encoded to have frames withdifferent compressed bit lengths. The frame memory 23 stores data of thedetected I-frames.

In other words, compressed digital data of the I-frames repeatedlypresent at intervals of n frames are separated from the encoded bitstream shown in FIG. 4 and then duplicatively recorded on a specifictrack because they can be independently decoded. A write enable signalW/E of high level is applied to the frame memory 23 only for the periodof detecting I-frames from the encoded bit stream by the frame detector24. As a result, the frame memory 23 can store only the compressed videodata of the I-frames.

This procedure for detecting I-frames will be described in detail, inconjunction with FIG. 12. An input bit stream is received in the framedetector 24 and then decoded. The frame detector 24 detects a frame markcode from a header of each frame in the bit stream. When the frame markcode is detected, an increment in frame counted value is carried out. IfI-frames are present at intervals of n frames, it is determined whetherthe number of counted frames equals a multiple of n (i.e., k*n, wherek=0, 1, 2, . . . ). When the (n*k)th is detected, a write enable signalW/E of high level is applied to the frame memory 23, thereby enablingcompressed digital data bits of a corresponding I-frame to be stored.When a next frame mark code is detected, a write enable signal W/E oflow level is applied to the frame memory 23. As a result, it is possibleto prevent frames of the frame bit stream other than I-frames from beingstored.

The frame recording position controlling unit 21 sends selectivelyI-frame data V23 and record data V22 outputted from the frame extractingunit 20 to the digital recording unit 18 at a predetermined timing.Accordingly, a recording format shown in FIG. 9 is formed in the digitalrecording unit 18.

On the other hand, since the lengths of compressed data of frames arenon-uniform, the frame memory 23 may encounter an underflow phenomenonthat data stored in the frame memory 23 at the moment an I-frame isrecorded in the frame memory 23 is insufficient or an overflowphenomenon that data stored in the frame memory 23 prior to recording ofan I-frame is full.

This will be descried in detail. Assuming that the average bit rate ofinput data received in the interface 1 is R and the size of regions ofthe input data occupied by I-frames is α, the average bit rate of datato be recorded is expressed by R+αR. This average bit rate of data iscalculated in the track number calculator 28. In this case, α can becalculated from α=the number of tracks i for I-frames/ the number oftracks j for P-frames. Here, the number of tracks, i, is generallydetermined by the average bit rate of I-frames.

The multiplexing timing generator 27 operates an output V28 of the tracknumber calculator 28 which calculates the number of I-frame tracks, i,and the number of P-frame tracks, j. The multiplexing timing generator27 also operates the output SWP of the drum pulse generator 7. By theseoperations, a reference pulse is calculated. One pulse of the output SWPof the drum pulse generator 7 corresponds to a recording period for onetrack in a case of recording one-channel data and to a recording periodfor two tracks in a case of recording two-channel data. Accordingly, themultiplexing timing generator 27 outputs a switching signal V27 enablingthe multiplexer 25 to selectively output data V23 for double speedstored in the frame memory 23 and normally-recorded data (FIG. 10B)buffered and amplified by the buffer 22, as shown in FIG. 10D.

In the output V22 from the buffer 22 shown in FIG. 10B, Δt representsthe period for delaying outputting of I-frames present between the firstrecording track and a predetermined track so as to prevent an underflowphenomenon. In the worst case where an underflow phenomenon occurred inthe frame memory 23, the bit stuffing unit 26 performs a bit stuffingoperation for adding, to data of I-frames, escape synchronous codes anddummy bits capable of being detected in reproduction, so as to generatedata having a constant length. On the other hand, where an overflowphenomenon occurred in the frame memory 23, a write enable signal W/E oflow level is applied from the frame detector 24 to the frame memory 23for a predetermined period.

In the frame position information recording unit 19, the frame positionrecorder 29 and the index signal recorder 30 receive the output V27'from the multiplexing timing signal generator 27 of the frame recordingposition controlling unit 21. The frame position recorder 29 outputsinformation V29 based on its frame position discrimination to therecording formatters 3A and 3B. Based on the information V29, therecording formatters 3A and 3B form a synchronous block includinginformation indicative of the position of a track including a nextI-frame recorded, in each video data region. The recording formatters 3Aand 3B also record the recording position information in the firstsynchronous block recording position of the tracks including I-framesrecorded, as shown in FIG. 9. Here, the recording position informationrepresents the code converted from the number of tracks present betweenthe track including the current I-frame recorded and the track includingthe next I-frame recorded, as shown in FIG. 11.

On the other hand, the index signal recorder 30 outputs indexinformation V30, namely, a pulse indicative of whether an I-frame hasbeen recorded or not, to the index head 31 which, in turn, records theindex information V30 on a control track.

The above-mentioned overall operations will be described in detail. Asthe head drum 6 carrying the heads HD1 to HD4 is rotated by the drivingforce of the drum motor M1 while the magnetic tape engaged between thecapstan 9 and the pinch roller 10 is fed by the driving force of thecapstan motor M2, the interface 1 receiving the input signal Vi such asthe compressed HDTV signal or the normal TV signal applies its output V1to the frame extracting unit 20. Thereafter, the recorded data isbuffered and amplified in the buffer 22 for a predetermined period whilethe I-frame data is stored in the frame memory 23 in accordance with thewrite enable signal W/E from the frame detector 24.

Subsequently, the multiplexer 25 receives selectively the output V22from the buffer 22 and the output V23 from the frame memory 23, based onthe output V27 from the multiplexing timing generator 27. As a result,the multiplexer 25 outputs the output signal V25 as shown in FIG. 10D tothe digital recording unit 18. Thereafter, the interleaving andchannel-dividing circuit 2 of the digital recording unit 18 interleavesthe signal V25 to a predetermined form for reducing burst errors andthen outputs signals V2 and V3 channel-divided to be matched with arecording channel bandwidth to the recording formatters 3A and 3B,respectively.

Accordingly, the recording formatters 3A and 3B form synchronous blocksshown in FIG. 6 so as to add synchronous signals SYNC, identificationsignals ID and error correction codes ECC. The recording formatters 3Aand 3B also form position information blocks of recording tracks, basedon the output V29 from the frame position recorder 29 in the frameposition information recording unit 19, thereby forming positioninformation about the first synchronous blocks of the tracks includingI-frames recorded.

Outputs V4 and V5 are converted to a predetermined recording format inthe channel modulators 4A and 4B, amplified to a predetermined level bythe recording amplifiers 5A and 5B, and then selectively sent to theheads HD1 (or HD3) and HD2 (or HD4) via the switches SW1 and SW2switched by the output SWP of the drum pulse generator 7 generated bythe rotation of the drum motor M1.

Thus, the outputs of the recording amplifiers 5A and 5B selectivelyapplied to the heads HD1 (or HD3) and HD2 (or HD4) via the switches SW1and SW2 being switched are recorded on the magnetic tape in a recordingformat shown in FIG. 9.

On the other hand, when a speed-varied reproduction mode is selected ina case where the data of the recording format shown in FIG. 9 has beenrecorded on the magnetic tape, the data recorded on the magnetic tape isreproduced in the digital reproduction unit 32. That is, signalsrecorded on the magnetic tape are detected by the heads HD1 (or HD3) andHD2 (or HD4) while the magnetic tape engaged between the capstan 9 andthe pinch roller 10 rotated by the capstan motor M2 travels on the headdrum 6 driven by the drum motor M1.

The signals detected by the heads HD1 (or HD3) and HD2 (or HD4) are sentto the reproduction amplifiers 11A and 11B via the switches SW3 and SW4switched by the output SWP of the drum pulse generator 7, respectively.The signals received in the reproduction amplifiers 11A and 11B areamplified to a predetermined level and then sent to the equalizers 12Aand 12B which, in turn, compensate distortions of frequencycharacteristics of the amplified signals V10 and V11, respectively.Resultant signals V12 and V13 from the equalizers 12A and 12B are thenapplied to the channel demodulators 13A and 13B which, in turn,demodulate the output signals V12 and V13 to the original signal forms,respectively.

Output signals V14 and V15 from the channel demodulators 13A and 13B arereceived in the sync-detecting and error-correcting circuits 14A and 14Bwhich, in turn, detect respectively synchronous signals SYNC andidentification signals ID from the received signals V14 and V15 andremove error components included in the recorded data. Resultant signalsV16 and V17 from the sync-detecting and error-correcting circuits 14Aand 14B are applied to the deinterleaving circuit 15A and 15B which, inturn, deinterleave the signals V16 and V17 to the original signal forms,respectively. Resultant signals V18 and V19 are then sent to thedeformatter 16 of the frame removing unit 35.

At this time, the frame position information detecting unit 33 detectsindex information recorded on a control track disposed at the lower edgeof the magnetic tape by the index head 31. The index information is apulse indicative of a track including an I-frame. On the other hand, therecording position-synchronized block detector 40 detects recordingposition-synchronized blocks recorded with I-frames from the outputs V16and V17 of the sync-detecting and error-correcting circuits 14A and 14B.Upon detecting the index information in order to achieve adiscrimination for the position of a specific track, the index signaldetector 36 takes into consideration the time taken to control a speedmatched with a speed multiple and calculated in the capstan servo speedcalculator 38 of the tape speed controlling unit 34. The physicalposition of the index head 31 is determined by the processing speed ofthe capstan servo speed calculator 38.

The recording position-synchronized block detector 40 also detects theoutputs V16 and V17 of the sync-detecting and error-correcting circuits14A and 14B and separates recording position-synchronized blocks shownin FIG. 11 from the detected signals V15 and V17. The recordingposition-synchronized block detector 40 outputs a signal 40 which isindicative of codes relating to the speed multiple and selected fromcodes indicative of relative positions and present in the separatedsynchronous blocks. The recording position decoder 39 decodes the signalV40 received from the recording position-synchronized block detector 40and the speed multiple n. An optional code DIFi present in eachsynchronous block is a code indicative of the number of tracks presentbetween the current track and the i-th track including specific datarecorded.

Accordingly, the frame position information detecting unit 33 detectsspecific track position information periodically or non-periodicallyrecorded and track position information about I-frames recorded in therecording position-synchronized blocks, taking into consideration thecalculation time taken to control the speed of the capstan motor M2 andthe driving time. In this connection, the capstan servo speed calculator38 receives the position information V36 from the index signal detector36 and the position information V39 from the recording position decoder39 and thereby calculates the rotation speed of the capstan motor M2 inaccordance with the input speed multiple n. Resultant signal V38 fromthe capstan servo speed calculator 38 is then applied to the capstanservo driving signal generator 37 which, in turn, controls the speed ofthe capstan motor M2 so that the capstan motor M2 can be drivenrepeatedly at a normal speed and a high speed. As a result, the headsHD1 to HD4 mounted on the drum 6 repeatedly travel at the normal speedon specific tracks of the magnetic tape and jump travel on other tracks,thereby enabling reproduction of speed-varied videos.

FIGS. 13A to 13C illustrate an example of a capstan servo speed controlin a case where speed-varied specific data have been recorded on everytwo-track at intervals of four tracks. In this case, the capstan motorM2 is driven two tracks at a normal speed in the same direction as therecording tracks for the first half of the initial cycle shown in FIG.13B. For the next half of the initial cycle, the capstan motor M2 isdriven four tracks at a high speed. During the accelerated driving, thecapstan motor M2 exhibits the driving characteristic shown in FIG. 13Abecause the output V37 of the capstan servo driving signal generator 37is periodically varied in level, as shown in FIG. 13C. By virtue of sucha speed-varied driving of the capstan motor M2, it is possible to reducean excessive characteristic of the capstan servo speed.

The outputs V18 and V19 from the digital reproduction unit 32 resultedfrom the speed-varied reproduction are sent to the deformatter 16 of theframe removing unit 35, converted into the signal form prior to therecording, and then outputted as a speed-varied reproduced signal Vosuch as a digital HDTV signal or a normal TV signal via the interface17.

For the signal conversion in the deformatter 16, it is required toremove the stuffing bits or dummy bits added for preventing theunderflow phenomenon of the frame memory 23 upon recording data forvaried speed on specific tracks. To this end, the stuffing bit-detectingand removing circuit 42 supplies a bit removing signal V42 forpreventing any bit string from being outputted to the interface 17 whena stuffing synchronous code recorded at the starting portion of stuffingbits is detected. The supplying of the bit removing signal V42 iscontinued until a stuffing bit end code is detected.

In the reproduction at the normal speed, the frame removing unit 35 alsoseparates data of recording tracks for varied speed so that the I-framedata recorded on the magnetic tape for the speed-varied reproduction isprevented from being outputted to the interface 17 and thereby beingincluded in the reproduced signal Vo.

On the other hand, the frame removal timing generator 41 receivesposition information of tracks recorded with specific data for variedspeed from both the recording position decoder 39 and the index signaldetector 36 of the frame position information detecting unit 33. Basedon the output SWP of the drum pulse generator 7 shown in FIG. 14A, theframe removal timing generator 41 then outputs a frame removing signalV41 shown in FIG. 14C to the deformatter 16.

Based on the frame removing signal V41, the deformatter 16 removesI-frame data from the signals V18 and V19 (FIG. 14B) received from thedeinterleaving circuits 15A and 15B of the digital reproduction unit 32.As a result, the deformatter 16 outputs a signal V20 shown in FIG. 14D,thereby enabling the reproduction at the normal speed.

As apparent from the above description, the present invention providesan apparatus for controlling recording and reproduction in a magneticVCR capable of separating specific data for a speed-varied reproductionfrom compressed digital video signals and recording them on designatedtracks in a recording mode, recording position information of thedesignated tracks on a control track by an index head or recordingposition information of recording position-synchronized blocks at thestarting portions of the designated tracks recorded with the specificdata so as to accurately scan the designated tracks in a reproductionmode, controlling a capstan servo speed so as to maintain the travel ofa magnetic tape at a normal speed and periodically or non-periodicallyaccelerate or decelerate it where specific data for varied-speed havebeen recorded periodically or non-periodically on predetermined portionsof tracks, thereby making heads travel repeatedly at the normal speedand the high speed and thereby detect continuously the specific tracksfor varied-speed. In accordance with the apparatus, the specific datafor a speed-varied reproduction is removed in the reproduction at thenormal speed. Thus, the reproduction at the normal speed can beaccomplished.

Accordingly, the present invention provides a repeatability ofreproduced video at a varied speed without any deterioration in picturequality in that it enables recording of specific data for speed-variedreproduction and continuous detection of the specific data in thespeed-varied reproduction.

Although the preferred embodiments of the invention have been disclosedfor illustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the scope and spirit of the invention as disclosed in theaccompanying claims.

What is claimed is:
 1. An apparatus for controlling recording andreproducing in a video cassette tape recorder comprising:frameextracting means for buffering compressed digital data input thereto,and extracting specific data for a speed-varied reproduction from saidcompressed digital data; frame recording position controlling means forcalculating a number of tracks for recording the compressed digital dataand selectively outputting a buffered output, said extracted specificdata from said frame extracting means, and a multiplexing timing signal;frame position information recording means for recording positioninformation of specific tracks for the speed-varied reproduction andindex information on a magnetic tape, based on said multiplexing timingsignal; digital recording means for recording digital signals includingsaid digital data and said index information on said magnetic tape;digital reproduction means for reproducing the digital signals recordedon the magnetic tape; frame position information detecting means fordetecting said position information of the specific tracks for thespeed-varied reproducing and said index information; tape speedcontrolling means for controlling the speed of a capstan motor, based onsaid detected index information and said position information of thespecific tracks; and frame removing means for receiving an output fromthe digital reproduction means and removing unnecessary bit streams fromthe specific data.
 2. An apparatus in accordance with claim 1, whereinsaid frame extracting means comprises:an interface for receiving saidcompressed digital data; a buffer for buffering an output of saidinterface for a predetermined period; a frame detector for detectingsaid specific data from said output of the interface and outputting awrite enable signal; and a frame memory for selecting and storing thedetected specific data, based on said write enable signal.
 3. Anapparatus in accordance with claim 2, wherein said frame detector countsa number of frames when a frame mark code is detected from a bit streamof said output of the interface, and enables said write enable signalwhen said counted number of frames is determined to be the same as aninterval number at which I-frames are present.
 4. An apparatus inaccordance with claim 1, wherein said frame recording positioncontrolling means comprises:a track number calculator for calculating anaverage bit rate of said compressed digital data, the size of thespecific data, a number of tracks for recording said specific data and anumber of tracks present between said specific tracks; a multiplexingtiming generator for receiving an output from said track numbercalculator and outputting a switching signal for positioning thespecific data on said specific tracks in accordance with a headswitching signal; a multiplexer for selecting an output from said frameextracting means, based on an output from said multiplexing timinggenerator and sending said selected output to said digital recordingmeans; and a bit stuffing circuit for filling insufficient data with bitstreams or dummy bits when said selected output of the frame extractingmeans is at an underflow state.
 5. An apparatus in accordance with claim1, wherein said frame position information recording means comprises:aframe position recorder for receiving an output from said framerecording position controlling means and outputting positiondiscrimination information to said digital recording means so as torecord position information of a next specific track on an initialsynchronous block of a track having said specific data recorded thereon;and an index signal recorder for recording position information of saidtrack having said specific data recorded thereon on a control track ofsaid magnetic tape by an index head.
 6. An apparatus in accordance withclaim 1, wherein said frame position information detecting meanscomprises:an index signal detector for detecting index informationrecorded on a control track of said magnetic tape, said indexinformation indicating whether tracks recorded with said specific dataare present; a recording position-synchronized block detector fordetecting an output from said digital reproduction means and detectingrecording position-synchronized blocks recorded with codes indicative ofrelative position information of said tracks recorded with said specificdata; and a recording position decoder for decoding an output of saidrecording position-synchronized block detector, based on a number ofdifferent tape speeds, and thereby outputting a signal for calculating acapstan servo speed.
 7. An apparatus in accordance with claim 1, whereinsaid tape speed controlling means comprises:a capstan servo speedcalculator for calculating a capstan servo speed for repeating a normalspeed travel on said specific tracks and a high speed travel on tracksbetween adjacent specific tracks in a speed-varied reproduction by usingthe position information of the specific track from said frame positioninformation detecting means based on a number of different tape speeds;and a capstan servo drive signal generator for controlling driving ofsaid capstan motor, based on an output of said capstan servo speedcalculator.
 8. An apparatus in accordance with claim 1, wherein saidframe removing means comprises:a deformatter for converting an output ofsaid digital reproduction means to a signal form prior to recording; astuffing bit-detecting and removing circuit for outputting a bitremoving signal to said deformatter and removing stuffing bits or dummybits added for preventing generation of an underflow of said frameextracting means in the speed-varied reproduction; and a frame removaltiming generator for receiving said position information of the specifictracks from said frame position information detecting means andoutputting a frame removing signal to the deformatter, based on a headswitching signal, thereby preventing outputting of said specific data ina normal-speed reproduction.
 9. An apparatus in accordance with claim 1,wherein said specific data includes I-frames.
 10. An apparatus inaccordance with claim 1, wherein said digital recording means and saiddigital reproduction means include a plurality of heads and switches forselectively recording and reproducing the digital signals.
 11. Anapparatus for controlling recording in a video cassette tape recordercomprising:frame extracting means for receiving compressed digital datainput thereto and extracting specific data for a speed-variedreproduction from said compressed digital data; frame recording positioncontrolling means for generating a multiplexing timing signal andmultiplexing said compressed digital data and said extracted specificdata from said frame extracting means based on said multiplexing timingsignal; frame position information recording means for recording indexinformation and position information of specific tracks for recordingsaid specific data for the speed-varied reproduction on a magnetic tapebased on said multiplexing timing signal; and digital recording meansfor recording digital signals including said digital data and specificdata from said frame recording position controlling means on themagnetic tape.
 12. An apparatus in accordance with claim 11, whereinsaid frame extracting means includes:an interface for receiving saidcompressed digital data; a buffer for buffering an output of saidinterface for a predetermined period; a frame detector for detectingsaid specific data from said output of the interface and outputting awrite enable signal; and a frame memory for selecting and storing saidspecific data based on said write enable signal.
 13. An apparatus inaccordance with claim 12, wherein said frame detector starts countingframes when a frame mark code is detected from a bit stream of saidoutput of the interface, and enables said write enable signal when saidcounted frame number equals an interval number at which I-frames arepresent.
 14. An apparatus in accordance with claim 11, wherein saidframe recording position controlling means includes:a track numbercalculator for calculating a number of said specific tracks forrecording said specific data and a number of tracks present between saidspecific tracks; a multiplexing timing generator for generating saidmultiplexing timing signal based on an output from said track numbercalculator; and a multiplexer for selecting an output from said frameextracting means based on said generated multiplexing timing signal. 15.An apparatus in accordance with claim 14, wherein said frame recordingposition controlling means includes a bit stuffing circuit for fillinginsufficient data with bit streams or dummy bits when said selectedoutput of the frame extracting means is at an underflow state.
 16. Anapparatus in accordance with claim 11, wherein said frame positioninformation recording means includes:a frame position recorder forreceiving an output from said frame recording position controlling meansand outputting position discrimination information to said digitalrecording means so as to record said position information of saidspecific tracks; and an index signal recorder for recording said indexinformation on a control track of the magnetic tape, said indexinformation including information indicating whether said specifictracks for said specific data are present.
 17. An apparatus inaccordance with claim 11, wherein said specific data includes I-frames,and said digital recording means includes a plurality of heads andswitches for selectively recording said digital signals.
 18. Anapparatus in accordance with claim 11, wherein said digital recordingmeans includes an interleaving and channel driving circuit, a pluralityrecording formatters, and a plurality of channel modulators, forformatting said digital signals so as to record said digital signals onthe magnetic tape.
 19. A method for controlling recording andreproduction in a video cassette tape recorder, comprising the stepsof:extracting specific data for a speed varied reproduction fromcompressed digital data; calculating a number of tracks for recordingsaid digital data and outputting a multiplexing timing signal based onsaid calculated number of tracks; recording position information ofspecific tracks for the speed varied reproduction and index informationon a magnetic tape based on said multiplexing timing signal; recordingdigital signals including said digital data and said index informationon the magnetic tape; reproducing said digital signals recorded on themagnetic tape; detecting said position information of the specifictracks for the speed varied reproduction and said index information;controlling the speed of a capstan motor based on said detected indexinformation and position information of the specific tracks; andremoving unnecessary bit streams from said specific data.
 20. A methodin accordance with claim 19, wherein said specific data includesI-frames.
 21. A method of controlling recording in a video cassette taperecorder, comprising the steps of:extracting specific data for aspeed-varied reproduction from compressed digital data; generating amultiplexing timing signal and multiplexing said compressed digital dataand said extracted specific data based on said multiplexing timingsignal; recording index information and position information of specifictracks for recording said specific data for the speed-variedreproduction on a magnetic tape based on said multiplexing timingsignal; and recording digital signals including said multiplexed digitaldata and specific data on the magnetic tape.
 22. A method in accordancewith claim 21, wherein said generating step includes calculating anumber of tracks for recording said digital data and generating saidmultiplexing timing signal based on said calculated number of tracks.